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Reaction Rates and Rate Law .txt | Now, we begin with two reactants, x and Y and they convert into W and Z. What elementary simply means is that they convert from reactants to products in a single step. Elementary reactions are some of the most basic reactions out there. Now notice that A-B-C and D are coefficients of each respective molecule and they represent the number of molecules or moles. Now, rates of reactions tell you how quickly reactants become products, so how quickly x and y become W and Z. In other words, the rate can be found by the change in concentration of reactants over some given time. |
Reaction Rates and Rate Law .txt | Now notice that A-B-C and D are coefficients of each respective molecule and they represent the number of molecules or moles. Now, rates of reactions tell you how quickly reactants become products, so how quickly x and y become W and Z. In other words, the rate can be found by the change in concentration of reactants over some given time. Now, notice that we go from a positive amount or some amount to a small amount. So over time, our x and y will disappear. So therefore, the rate of these guys are negative because remember, we're subtracting our initial from final. |
Reaction Rates and Rate Law .txt | Now, notice that we go from a positive amount or some amount to a small amount. So over time, our x and y will disappear. So therefore, the rate of these guys are negative because remember, we're subtracting our initial from final. An initial concentration of x is larger than final concentration of x. The final will be less. We'll have less x and y at the end because some of these guys will convert to W and Z. |
Reaction Rates and Rate Law .txt | An initial concentration of x is larger than final concentration of x. The final will be less. We'll have less x and y at the end because some of these guys will convert to W and Z. So once again, the rate or average rate of x is negative change in concentration of x over time. Now, time is also multiplied by A. Now, for the case that A-B-C and D are one, we simply take away the A, because one times T is T. So the same thing can be said for w for Y. |
Reaction Rates and Rate Law .txt | So once again, the rate or average rate of x is negative change in concentration of x over time. Now, time is also multiplied by A. Now, for the case that A-B-C and D are one, we simply take away the A, because one times T is T. So the same thing can be said for w for Y. The negative change in concentration of y over BT gives you the rate of disappearance of Y. Now, the rate of appearance of W and Z can be given by these formulas where now we have the positive because these guys appear and so these guys will both be positives. Now, let's look at the factors affecting our reaction rates. |
Reaction Rates and Rate Law .txt | The negative change in concentration of y over BT gives you the rate of disappearance of Y. Now, the rate of appearance of W and Z can be given by these formulas where now we have the positive because these guys appear and so these guys will both be positives. Now, let's look at the factors affecting our reaction rates. So, we already said that temperature affects our rates of reaction because it affects our rate constant. Now, if the rate constant increases, then our rate of reaction increases. And we'll see why at the end of this lecture. |
Reaction Rates and Rate Law .txt | So, we already said that temperature affects our rates of reaction because it affects our rate constant. Now, if the rate constant increases, then our rate of reaction increases. And we'll see why at the end of this lecture. But notice that temperature increasing. Temperature affects rate constant by affecting the kinetic energy of molecules. On average, molecules will have higher kinetic energy and a higher temperature. |
Reaction Rates and Rate Law .txt | But notice that temperature increasing. Temperature affects rate constant by affecting the kinetic energy of molecules. On average, molecules will have higher kinetic energy and a higher temperature. And that means they will be more likely to overcome the activation energy barrier and become our products. Now, concentrations we see using these formulas affect or increase our rates. In other words, if we have higher concentration, if this guy becomes higher, this guy becomes higher, if this guy becomes higher and this guy becomes higher, our rates will increase. |
Reaction Rates and Rate Law .txt | And that means they will be more likely to overcome the activation energy barrier and become our products. Now, concentrations we see using these formulas affect or increase our rates. In other words, if we have higher concentration, if this guy becomes higher, this guy becomes higher, if this guy becomes higher and this guy becomes higher, our rates will increase. Now, pressure also has an effect on rates and we'll see how in another video. Now we spoke about elementary reactions in which reactants become products in a single step. Now, there are also multi step reactions and those include many different steps, intermediate steps. |
Reaction Rates and Rate Law .txt | Now, pressure also has an effect on rates and we'll see how in another video. Now we spoke about elementary reactions in which reactants become products in a single step. Now, there are also multi step reactions and those include many different steps, intermediate steps. However, we can use this guide or this formula to approximate our rates of multistep reactions as long as the concentrations of intermediates are held relatively low. Now that means suppose we have the following reaction a plus B react to form intermediate AB and then that intermediate AB reacts with C, some other guy to form ABC. Now this guy is out intermediate. |
Reaction Rates and Rate Law .txt | However, we can use this guide or this formula to approximate our rates of multistep reactions as long as the concentrations of intermediates are held relatively low. Now that means suppose we have the following reaction a plus B react to form intermediate AB and then that intermediate AB reacts with C, some other guy to form ABC. Now this guy is out intermediate. Now, as long as the concentration of this guy is kept relatively low, we can approximate using these formulas here. So likewise, the rate of change or disappearance of A and B can be given by negative change in concentration of B divided by T. Now that only works if that intermediate concentration is kept low. Now let's talk about the rate law. |
Reaction Rates and Rate Law .txt | Now, as long as the concentration of this guy is kept relatively low, we can approximate using these formulas here. So likewise, the rate of change or disappearance of A and B can be given by negative change in concentration of B divided by T. Now that only works if that intermediate concentration is kept low. Now let's talk about the rate law. The rate law is a mathematical representation that summarizes relationship between reactants and reaction rate. And it also builds a relationship between our rate constant and our rate of reaction. Now notice in this reaction we have a forward reaction and a reverse reaction. |
Reaction Rates and Rate Law .txt | The rate law is a mathematical representation that summarizes relationship between reactants and reaction rate. And it also builds a relationship between our rate constant and our rate of reaction. Now notice in this reaction we have a forward reaction and a reverse reaction. Now, we're only going to worry about the forward reaction, but know that if there is a forward reaction, there could also be a reverse reaction. Now let's look at the rate law. The rate law is this entire equation or relation. |
Reaction Rates and Rate Law .txt | Now, we're only going to worry about the forward reaction, but know that if there is a forward reaction, there could also be a reverse reaction. Now let's look at the rate law. The rate law is this entire equation or relation. So rate of the forward reaction of this reaction is given by our rate constant KF for the forward reaction times the concentration of X to the A power. In this case this A times the concentration of Y to the B power B. Now, the reason we chose A and B is because this is an elementary reaction. |
Reaction Rates and Rate Law .txt | So rate of the forward reaction of this reaction is given by our rate constant KF for the forward reaction times the concentration of X to the A power. In this case this A times the concentration of Y to the B power B. Now, the reason we chose A and B is because this is an elementary reaction. Now, if this was not an elementary reaction, we would not be able to use this A and B the way we did here. Now for now, we're only going to worry about elementary reactions. So this is our rate law. |
Reaction Rates and Rate Law .txt | Now, if this was not an elementary reaction, we would not be able to use this A and B the way we did here. Now for now, we're only going to worry about elementary reactions. So this is our rate law. Now this KF, our rate constant depends strictly on temperature and types of reactants. It does not depend on the concentrations of reactants nor products. Now, we saw from another video that KF is known as the Iranians equation and it depends strictly on temperature. |
Reaction Rates and Rate Law .txt | Now this KF, our rate constant depends strictly on temperature and types of reactants. It does not depend on the concentrations of reactants nor products. Now, we saw from another video that KF is known as the Iranians equation and it depends strictly on temperature. So at the same temperature we're going to use the same reactant for some given reaction. Now, if we change our reactants, we're also going to have to change our KF because our rate constant also depends on the types of reactants used. Now, one last thing I want to mention is that this rate law, this equation is determined strictly using experimental results. |
Reaction Rates and Rate Law .txt | So at the same temperature we're going to use the same reactant for some given reaction. Now, if we change our reactants, we're also going to have to change our KF because our rate constant also depends on the types of reactants used. Now, one last thing I want to mention is that this rate law, this equation is determined strictly using experimental results. That's the only way we can determine this relation. We can't determine this relation using the formula above. |
Reaction Rates and Rate Law .txt | That's the only way we can determine this relation. We can't determine this relation using the formula above. |